1. Field of the Invention
The present invention relates to a method for manufacturing a germanium epitaxial layer and a method for manufacturing a device using the same, and more particularly, to a method for manufacturing a germanium epitaxial layer and a method for manufacturing a device using the same with performing a deposition process and an annealing process alternately at least two times.
2. Description of the Prior Art
Conventional optical devices, such as an avalanche photodiode (APD), which uses germanium to absorb light, can detect a weak light signal or receive a light signal that has traveled a long distance. In the conventional avalanche photodiode, a germanium epitaxial layer is formed on the diode formed by a silicon epitaxial layer and serves as a light absorption layer. When the germanium epitaxial layer absorbs few photons, the avalanche breakdown occurs in the germanium epitaxial layer by applying a reverse bias across the diode, and the photons in the germanium epitaxial layer will generate multiple current. Therefore, the current which represents the light signal can be detected. However, the germanium epitaxial layer in the conventional avalanche photodiode requires a certain thickness, thereby having high defect density. Accordingly, an over high dark current in the avalanche photodiode will be generated, and the accuracy of detection of the avalanche photodiode will also decrease due to the over high defect density.